Oxidant,antioxidant and physical exercise

Generation of reactive oxygen species (ROS) is a normal process in the life of aerobic organisms. Under physiological conditions, these deleterious species are mostly removed by the cellular antioxidant systems, which include antioxidant vitamins, protein and non-protein thiols, and antioxidant enzymes. Since the antioxidant reserve capacity in most tissues is rather marginal, strenuous physical exercise characterized by a remarkable increase in oxygen consumption with concomitant production of ROS presents a challenge to the antioxidant systems.An acute bout of exercise at sufficient intensity has been shown to stimulate activities of antioxidant enzymes. This could be considered as a defensive mechanism of the cell under oxidative stress. However, prolonged heavy exercise may cause a transient reduction of tissue vitamin E content and a change of glutathione redox status in various body tissues. Deficiency of antioxidant nutrients appears to hamper antioxidant systems and augment exercise-induced oxidative stress and tissue damage. Chronic exercise training seems to induce activities of antioxidant enzymes and perhaps stimulate GSH levels in body fluids. Recent research suggest that supplementation of certain antioxidant nutrients are necessary for physically active individuals.     

Functional interaction trap: a strategy for validating the functional consequences of tyrosine phosphorylation of specific substrates in vivo

Protein tyrosine phosphorylation controls diverse signaling pathways, and disregulated tyrosine kinase activity plays a direct role in human diseases such as cancer. Because activated kinases exert their effects by phosphorylating multiple substrate proteins, it is difficult or impossible to assess experimentally the contribution of a particular substrate to a cellular response or activity. To overcome this problem, we have developed a novel approach termed the "functional interaction trap," in which two proteins are induced to interact in a pairwise fashion through an engineered, highly specific binding interface. We show that the functional interaction trap can be used to direct a modified tyrosine kinase to specifically phosphorylate a single substrate of choice in vivo, permitting analysis of the resulting biological output. This strategy provides a powerful tool for validating the functional significance of tyrosine phosphorylation and other post-translational modifications identified by proteomic discovery efforts.     

Differential Lowering by Manganese Treatment of Activities of Glycolytic and Tricarboxylic Acid (TCA) Cycle Enzymes Investigated in Neuroblastoma and Astrocytoma Cells Is Associated with Manganese-Induced Cell Death

Manganese (Mn) is a trace metal required for normal growth and development. Manganese neurotoxicity is rare and usually associated with occupational exposures. However, the cellular and molecular mechanisms underlying Mn toxicity are still elusive. In rats chronically exposed to Mn, their brain regional Mn levels increase in a dose-related manner. Brain Mn preferentially accumulates in mitochondria; this accumulation is further enhanced with Mn treatment in vivo. Exposure of mitochondria to Mn in vitro leads to uncoupling of oxidative phosphorylation. These observations prompted us to investigate the hypothesis that Mn induces alterations in energy metabolism in neural cells by interfering with the activities of various glycolytic and TCA cycle enzymes using human neuroblastoma (SK-N-SH) and astrocytoma (U87) cells. Treatments of SK-N-SH and U87 cells with MnCl2 induced cell death in these cells, in a concentration- and time-dependent manner, as determined by MTT assays. In parallel with the Mn-induced, dose-dependent decrease in cell survival, treatment of these cells with 0.01 to 4.0 mM MnCl2 for 48 h also induced dose-related decreases in their activities of hexokinase, pyruvate kinase, lactate dehydrogenase, citrate synthase, and malate dehydrogenase. Hexokinase in SK-N-SH cells was the most affected by Mn treatments, even at the lower range of concentrations. Mn treatment of SK-N-SH cells affected pyruvate kinase and citrate synthase to a lesser extent as compared to its effect on other enzymes investigated. However, citrate synthase and pyruvate kinase in U87 cells were more vulnerable than other enzymes investigated to the effects of Mn. The results suggest the two cell types exhibited differential susceptibility toward the Mn-induced effects. Additionally, the results may have significant implications in flux control because HK is the first and highly regulated enzyme in brain glycolysis. Thus these results are consistent with our hypothesis and may have pathophysiological implications in the mechanisms underlying Mn neurotoxicity.     

Java Treeview--extensible visualization of microarray data

Open source software encourages innovation by allowing users to extend the functionality of existing applications. Treeview is a popular application for the visualization of microarray data, but is closed-source and platform-specific, which limits both its current utility and suitability as a platform for further development. Java Treeview is an open-source, cross-platform rewrite that handles very large datasets well, and supports extensions to the file format that allow the results of additional analysis to be visualized and compared. The combination of a general file format and open source makes Java Treeview an attractive choice for solving a class of visualization problems. An applet version is also available that can be used on any website with no special server-side setup.     

Functional integrity and structural stability of freeze-dried ectomycorrhizal fungi established through viability assays

Lyophilized vegetative mycelium of ectomycorrhizal fungi was subjected to various viability tests to confirm functional integrity. Physical integrity of freeze-dried cultures was comparable to that of non-lyophilized cultures. Inter- and intraspecific variations in morphology, physiology, and metabolic rate were maintained after lyophilization. Maintenance of total protein content confirmed metabolic stability. According to the assays of viability, a plating assay and determination of total biomass confirmed stable mitotic activity of the freeze-dried cultures.